The present invention relates in general to burnable coils for the control of insects, and more particularly to a method of and apparatus for zone treating or tip dosing coils during their manufacture.
Insect coils for controlling mosquitoes and other flying insects are well known. Conventional coils are typically manufactured by preparing a dough made up of materials that, when dry and ignited, will slowly burn releasing an insecticide into the atmosphere. The active insecticide ingredient is typically uniformly disbursed in the dough during blending of the dough ingredients, or by surface treating the dough. In general, there are four basic components of an insect coil, namely, an active insecticide ingredient, an organic filler capable of smoldering well, a binder, and additives such a dye or a fungicide. Coils are formed usually as a sheet of material cut or otherwise formed into a spiral shape. For economy of operation and strength of the resulting coils it is convenient to cut the sheet of material in a coil within a coil pattern, i.e. two coils one within the other which, when dried, can be simply separated by gently disengaging one from the other. As an example, see U.S. Design Patent 385,942.
D'Orazio U.S. Pat. No. 4,114,318 is a typical example of a conventional insect coil. D'Orazio describes the formation of a sheet of dough throughout which insecticide is uniformly mixed. The sheet of dough is subsequently formed into the desired coil shape. Another example is Elsner et al. U.S. Pat. No. 5,447,713 which illustrates a board of dough from which coil shapes are punched or cut. Elsner et al. also describes the surface treatment of the board of dough or of the punched out coil with a layer of insecticide uniformly and continuously applied with rollers.
When the outermost end or tip end of a conventional coil is lit, the active ingredient in the coil located immediately beside the burning tip end is heated and volatizes. Conventional coils traditionally have been valued in part for their ability to deliver a continuous, linear discharge of volatile active insecticide ingredient over a considerable length of time, i.e. 3-8 hours or more, in order to control insects, especially mosquitoes.
It is also known that zone treating or tip dosing of insect coils yields performance advantages. See for example Flashinski et al. U.S. Pat. No. 6,419,898 and Kandathil et al. U.S. Pat. No. 5,657,574. By this means, the coil is made to deliver an active insecticide ingredient at a greater rate when it is first lit. This higher initial dose of active insecticide ingredient is intended to quickly establish an effective insect controlling level of active insecticide ingredient in the previously untreated air in the vicinity of the coil. Kandathil et al. accomplishes this goal by utilizing a greater cross-sectional area near its tip end, while Flashinski et al. accomplishes a similar goal by applying an auxiliary coating of the active insecticide ingredient at the tip end of the coil.
While it is advantageous to zone treat or tip dose an insect coil, it is difficult to precisely place the extra dose on the coil during the manufacture of such coils, especially in a high-speed automated process. In such a process, a sheet of dough travels through a cutting machine, and a cutter or die presses down or stamps into the dough from above cutting out the desired shape of the coil. Since the dough is still wet, the cut coil remains in the die while the die lifts and swivels so as to locate the now cut coils above a drying pan, and then lowers the cut coil toward the pan. An ejector plate pushes the cut but still wet coil out of the die allowing it to drop to the drying pan. The ejector is substantially the shape of the coil so that the entire still wet coil is uniformly ejected from the die. The pan which is also typically on a conveyor then is moved to a drying oven where the coil is dried.
Typically, as noted above, an insecticide is uniformly mixed into the dough before the coils are cut, although it is also known to apply active to the surface of a dry coil by spraying or rolling the active insecticide ingredient onto the surface of the coil. In any event, if one desires to add an extra dose of active to a specific location on the coil, whether the coil is wet or dry, it is necessary to orient the coil so that a sprayer or other dosing mechanism will be precisely over the location that is to receive the extra dose. Automated means of orientating the coils depend on interacting with the shape of the coils. However, mechanical orientating devices yield in-exact results, especially for standard, essentially round spiral coils which is due in part because coils dry to slightly different sizes, or may warp slightly upon drying, and in general have variations in shape. Any error in precise orientation of the coils with respect to the dosing mechanism causes errors in dose location, resulting in a unacceptably large number of defective coils.